30ft 1890's navy steam launch 1/6th scale

[tghs]

i"m just glad I didn't have to make two of the pump blocks

[cnr6400]

Craps is one thing - cards are another. At least you know Slim's got nothing up his sleeve, if playing cards - and no sleeve, either!   

[tghs]

started carving the blocks, the set of ball end mills are working great for this,, measured out the jig rods and started one on the unimat and quickly stopped, job much better suited for the atlas (I can turn one rod and part it into two needed) I won a book of ebay under  $20.00 total shipped, 1902 I.C.S Reference Library "Steam Engines and Steam Pumps" lots of good info and drawings, did find a drawing for a porting arrangement for a steam pump that I am looking at very hard,, the idea in that a small amount of steam is "trapped" during exhaust acting as a buffer to limit the piston travel,, seeing that my steam passages will be by an intermediate plate this would be easy to do..

[tghs]

chucked up a section of steel rod in the old atlas and turned the "jig" rods.. slim said they looked like ram rods for cannons and said he could do a "jig" he says lots of things

[crueby]

Thats an interesting arrangement for the porting on the cylinder. Would it really give a buffer though - the slide valve should be opening the end the piston is moving towards to steam by the time the piston got to the end? Might still be of  help if the pump was not fully primed and there was air in it.   

[tghs]

that valve motion would be true for an eccentric driven valve but this valve is moved by the other cylinders shaft motion,, will be scratching my head on this for a bit..

[Admiral_dk]

It might work nicely - but I can't tell as I'm missing a connection between the upper and lower "control axle" on the last drawing ...!...  does it connect linearly or digitally, so to speak ?

[tghs]

it's kind of one of things that doesn't translate well in a 3 view drawing..

[Admiral_dk]

OK - I didn't see that one comming .... and by the way, if left excatly as shown in the drawing - nothing will happen.

It's kind of funny construction - you can view it as a mix of "digitally" and analog control.
Lets say that the piston  shown in the drawing is moving to the right. When it has gone past midway trawel it will open for the steam that moves the hidden piston toward the left and it will have to wait for the hidden piston to go past its midway travel, before it get steam to move to the left.
This also means that depending on load it will either move in a very jerky (Digital) way or more and more toward a smooth movement with the pistons in a 90 degree phase differense.
Please don't ask me how much load to achive smooth movement as I don't have a clue - it's just what I expect from a dampened Oscillator.

[tghs]

set up the rotary table on the mill today( the new home made mounting fixtures worked great) by centering the four jaw chuck and then moving the jaws to put each port under the center the pump block was roughed out.. lots more work to be done on it, but it is looking less like a cube of brass..taking my old book and drafting tools home for the weekend..

[tghs]

here's  one I didn't see coming. had some conversations with the full scale steam guys that have been helping me,(these little pumps did use the dual porting!) they call the valve actuation I'm working towards external cross-over,, why? because an internal cross-over exist,, what a bit of watch-making even in full scale!! staying with the cole's model method of handling the valves with the duel porting..

[crueby]

Gack - that is a lot of levers inside that cover! I can see why you would lean towards the external levers.  I think it was on the Southworth pump thread that I worked out how they did the steam passages inside the block so they cross over, and the levers/valves can be normal straight-line ones. Just some drilling to lay out, but no fancy Harry-Potter-Goblin-Safe levers to make!

[tghs]

did some more shaping both ends of the feed pump.. they are starting to look less like blocks,, need to get the holes threaded for the valve covers and pipe fittings while there are still some good flat sections.. made an arbor for the cylinder block for use in the rotary table on the mill..  looks like there will be lots of dremel machining ahead..

[tghs]

started work on the the steam chest,, milled out the main section, the rod guides/glands will be a small lathe projects and soldered into bored holes..

[crueby]

Coming along great. I like how the steam chest bolts down on the outside rather than through the rim.